[0/2] add flag for tracking bio allocation

Message

Johannes Thumshirn March 21, 2019, 12:30 p.m. UTC

Hannes recently sent a patch in [1] to fix an Oops caused by
__blkdev_direct_IO_simple() doing bio submissions from the stack and which
ended up being freed bio bio_free(). As bio_free() expected a bio which was
allocated by bio_alloc_bioset() it crashed.

I've sent out a different aproach to tackling this problem and both Jens and
Jan leaned to my solution, namely adding another bio flag tracking the
allocation.

As flag is the last available bit, add a compile time check as a safety net,
so we're not accidentially overriding the high 3 bits of bi_flags, which are
used for the BVEC_POOL_IDX().

Note, Jens also staged a patch in his io_uring-next branch taking the last
flag. For this reason patch 2/2 might not be applied in this form, but 1/2 is
still applicable then.

[1] https://lore.kernel.org/linux-block/[e-mail]/

Johannes Thumshirn (2):
  block: bio: ensure newly added bio flags don't override BVEC_POOL_IDX
  bio: introduce BIO_ALLOCED flag and check it in bio_free

 block/bio.c               | 12 ++++++++++++
 include/linux/blk_types.h | 32 ++++++++++++++++++--------------
 2 files changed, 30 insertions(+), 14 deletions(-)